1. Field of the Invention
This invention is in the field of passenger restraint systems with tethers for securing the vehicle seat.
2. Description of the Prior Art
Three point restraint systems are used to secure a passenger within a vehicle seat. Typically, the system includes a seat belt extendable from a retractor with the outer end of the belt attached to one side of the seat. A tongue slidably mounted to the belt between the belt outer end and the retractor may then be pulled with the belt across the passenger and lockingly engage a buckle secured to the opposite side of the seat. In an emergency stop or crash, the retractor is operable to prevent further protraction of the belt thereby securing the passenger to the seat.
In an emergency stop or crash, the vehicle seat may pivot or move relative to the vehicle floor. Thus, in the event the passenger restraint system is mounted directly to the seat then the seat with passenger may move relative to the vehicle floor contacting conceivably the vehicle. Likewise, in the event the restraint system is secured to the vehicle then force resulting from the seat moving relative to the vehicle will be directed against the passenger who is held by the belt. As a result, various tether systems have been incorporated to prevent or limit the motion of the seat relative to the vehicle during a crash. A typical tether includes a cable extending between the vehicle seat and frame. A disadvantage of such a tether is that the seat is no longer movable to allow for adjustment of the positioning of the seat, U.S. Pat. No. 4,488,754 issued to Max Heesch et al. addresses the problems inherent in a fixed tether by allowing the seat frame to normally slide along a horizontally extending wire cable during seat adjustment while having a clamp engaging the wire cable during a crash preventing movement of the seat frame relative to the vehicle floor. The clamp is activated during the crash when the seat occupant force is applied to the clamp via the seat belt. Such a mechanism allows for horizontal adjustment of the seat while providing a tether between the seat and vehicle floor; however, vertical adjustment of the seat is precluded.
Another approach to provide an adjustable tether is by mounting a belt retractor to the vehicle and attaching the outer end of the belt fixedly to the seat thereby allowing the seat to be moved during normal adjustment but preventing movement of the seat relative to the vehicle during a crash. Such a combination of retractor and seat is disclosed in the commonly owned U.S. Pat. No. 5,015,010 issued to Homeier et al.
The U.S. Pat. No. 4,225,184 issued to Strowick discloses an anchoring arrangement for a safety belt located on a vehicle seat which is both vertically and longitudinally adjustable relative to the vehicle. The clamping force is achieved by a plurality of intermeshing gears activated by passenger force on the belt. Another approach is disclosed in the U.S. Pat. No. 4,229,041 issued to Werner wherein a plate is pivoted by passenger belt force against a guide rail which allows for adjustable movement of the seat. Yet a further design is disclosed in the U.S. Pat. No. 4,248,480 issued to Koucky et al. The Koucky et al design has a lever pivoted by passenger belt force against a rack fixed to the vehicle. It is known to attach a cable wound on a reel fixed to the vehicle with the outer end of the cable fixed to the back portion of the seat, such as shown in the German Offenlegungsschrift DE 3813557 A1.
Disclosed herein is an automatic locking tether which includes many of the advantages of the separate tethers previously described while having additional advantages. Our tether includes gripping means mounted to the seat which is lockingly engageable with a web extending upwardly from the vehicle. Normally, the gripper is not clamped to the web allowing for vertical and horizontal adjustment of the seat. The web gripper is triggered by buckle load resulting from passenger load or movement. The gripper is therefore immediately locked to the web which is taut eliminating activation of the lock at a source remote from the passenger such as at the location of the retractor.